A440 (concert A)
The A above middle C tuned to 440 Hz, the most widely used reference pitch for tuning ensembles and instruments.
Also called: A440, concert A, A = 440 Hz, 440 Hz
A440 is the note A4, the A above middle C, tuned to a frequency of 440 Hz. Ensembles tune to it so that players on different instruments sound the same pitch. It is the most widely used reference pitch today, though orchestras have tuned to other values at different times. Middle C, C4, sounds at about 261.6 Hz, so A4 lies a major sixth above it. Each semitone is a factor of 2 to the power 1/12, so the A an octave higher, A5, is 880 Hz and the A an octave lower, A3, is 220 Hz. The reference is a convention rather than a law of nature. Many period ensembles tune lower, to about 415 Hz, to match historical instruments.
Related terms
- Concert pitchThe actual sounding pitch of a note, as opposed to the pitch written for a transposing instrument.
- FrequencyThe number of complete vibration cycles per second, measured in hertz (Hz), which sets a sound's pitch.
- PitchThe perceived highness or lowness of a sound, which for most sounds follows its fundamental frequency.